Gallium nitride based structures are recognized as a promising material for short wavelength optoelectronic devices and high-power, high-frequency electronic devices. However, the potential of this material has been limited by the lack of a suitable lattice matched substrate for epitaxially grown device layers. This has led to the development of bulk GaN substrates. With the development of these substrates, surface preparation techniques must also be investigated to provide atomically smooth, damage-free surfaces, such as chemical mechanical planarization (CMP). Additionally, alternative processes that may further expand GaN technologies, including wafer bonding, and layer transfer techniques, often require planarization steps creating a need for a well-controlled GaN CMP process.
CMP uses a combination of chemical and mechanical reactions to remove material leaving a planarized, damage-free surface. Ideally, material removal is achieved by chemically altering the surface to a mechanically weaker form. This material is then abraded from the surface leaving the bulk undisturbed. Planarization occurs due to the acceleration of both mechanical grinding and chemical transformation at the high points. While CMP slurries have been developed to achieve angstrom level surface roughness, a need exists for improved CMP slurries.